Lost mould for producing a cylindrical bushing sleeve

ABSTRACT

A cylindrical bushing sleeve or another cast part, in particular a ring carrier for pistons, has a rough surface so that the surrounding cast material can cling to the cast part as required. The rough surface is created by producing the cast part with the aid of a lost mold provided with a particulate layer.

CROSS REFERENCE TO RELATED APPLICATIONS

Applicants claim priority under 35 U.S.C. §119 of German Application No.199 58 185.1 filed Dec. 2, 1999. Applicants also claim priority under 35U.S.C. §120 of PCT/EP00/11330 filed Nov. 16, 2000. The internationalapplication under PCT article 21(2) was not published in English.

The invention relates to a lost mold for production of a cylinder lineror of other cast parts, especially ring carriers for pistons, and to acorresponding production method as well as to cylinder liners producedwith inventive lost molds and to a composite of a plurality of cylinderliners and other cast parts.

The production of cylinder liners with lost molds is known in itselffrom, for example, German Patent (DE) 3909521 A. The production of whatare known as rough cast liners from cast iron is also known. In theprocess the rough surface provided with undercuts is made by a specialslip.

A corresponding method for aluminum liners is not yet known.

The invention therefore deals with the problem of providing a method anda corresponding lost mold for production of a cast liner, especially ofaluminum, having a rough outside surface.

This problem is solved by a lost mold according to the invention.Advantageous improvements are discussed below.

The inner core of this lost mold and the particles can be made, forexample, from polystyrene. Of course, all other materials that aresuitable for lost molds can also be considered.

By virtue of the structured surface of the lost mold formed fromparticles, a rough surface with undercuts is obtained during casting ofthe liner. During subsequent production of a cylinder block, an aluminumalloy is cast around this surface, thus achieving a clinging effectbetween liner and base material. The structured surface of the lost moldcan also be described as a particle layer permeated with holes on theinner mold of the lost core. An inventive layer differs from thegenerally common understanding of the word “layer”, however, in thatcohesion is usually absent between the individual particles forming thelayer and exists only between the inner core and the particles. Thelayer thickness is defined as the radial distance between the surface ofthe inner core and the extreme outer point of a particle.

The proportion of such holes, or in other words the surface not coveredwith particles, can have values ranging between 0% and 95% of the totalarea. Furthermore, it is also possible to provide the particles onlylocally, for example in an upper and a lower region of the inner core ofthe lost mold.

It is indeed known from EP 807479 A that a lost-foam core to be providedwith a spray-metallized layer can be provided with an intermediate layerof a spray-resistant plastic such as polyamide and, during spraying ofthe polyamide layer, simultaneously there can be introduced metalparticles, which remain as a structured metal layer during outgassing ofthe polyamide layer and are intended to improve the clinging of thespray-metallized layer to the material cast therearound, but this methodis not comparable with the present method. In particular, duringproduction of a corresponding layer by spraying, a good bond between themetal particles present in the intermediate layer and thespray-metallized layer can hardly be developed, since the differencebetween the melting points of the metal particles and plastic particlesis too different.

The invention will be explained in more detail hereinafter on the basisof an example, wherein:

FIG. 1 shows an inventive lost mold in cross section.

Lost mold 1 comprises an inner core 2 and a layer 3, which is formedfrom particles, contains holes and represents on the whole a structuredouter surface of lost mold 1. These particles do not have any cohesionwith one another, and thus are bonded only to inner core 2.

Layer 3 formed from particles is applied on inner core 2 by a process inwhich inner core 2 is first sprayed or painted with an adhesive or inwhich an adhesive is applied by rolling, after which the inner core isbrought into contact with the particles, for example by rolling innercore 2 in a bed of loose particles.

Since the particles are usually round, only point contact with innercore 2 is established in most cases. In a sectional diagram, therefore,a particle that has contact at a point disposed above the plane of thefigure can be illustrated diagrammatically as a particle that is not incontact with inner core 2.

The layer thickness of particle layer 3 as defined hereinabove isindicated in the drawing by a broken line.

The particles may have average diameters of 0.5 to 2 mm. The lost moldmay be used to make a cylinder liner of hypereutectic AlSi alloy, graycast iron or cast steel having a structured surface.

What is claimed is:
 1. A lost mold for production of a cylinder liner orcylinder-liner composite by casting technology, comprising in particularan aluminum alloy, or for production of a cast part by castingtechnology, in particular a ring carrier for pistons, the lost moldhaving an inner core, and being provided in the region of its outsidesurface with a surface structure having undercuts formed by particlesbonded adhesively to the inner core, said particles having averagediameters of 0.5 to 2 mm, and said outside surface of the lost moldbeing coated with a slip.
 2. A lost mold according to claim 1, whereinthe particles are bonded to the inner core by means of an adhesive.
 3. Alost mold according to claim 1, wherein the surface structure is formedon the whole by a particle layer that has lower average density than thedensity of the inner core.
 4. A cylinder liner of hypereutectic AlSialloy comprising a structured surface created by a lost mold accordingto claim
 1. 5. A cast part, especially a ring carrier for a piston,comprising a structured surface created by a lost mold according toclaim
 1. 6. A method for production of a lost mold for a cast cylinderliner made of an aluminum alloy and having a rough surface, comprisingthe steps of producing an inner core of the lost mold in the form of atubular segment, applying a particle layer onto the inner core, theparticles having average diameters of 0.5 to 2 mm and being bonded tothe inner core by adhesion and the particle layer having lower densityon the whole than the inner core; and coating the lost mold with a slip.